Fingerprint-sensing apparatus

ABSTRACT

A fingerprint-sensing apparatus is provided. The fingerprint-sensing apparatus includes a fingerprint-sensing pixel array and a plurality of read-out circuits. The fingerprint-sensing pixel array has a plurality of fingerprint-sensing pixel columns, and each of the plurality of fingerprint sensing pixel columns includes a plurality of fingerprint-sensing pixels. Each of the plurality of fingerprint-sensing pixels includes a scanning switch and a thermosensitive current generation circuit. The scanning switch is controlled by a row scanning signal. The thermosensitive current generation circuit generates a thermosensitive current according to the fingerprint-sensing pixel corresponding to a fingerprint ridge or a fingerprint valley. The plurality of read-out circuits is respectively coupled to the plurality of fingerprint-sensing pixel columns. The read-out circuits receive the thermosensitive current provided by the fingerprint-sensing pixels and generate a fingerprint-sensing signal according to the thermosensitive current.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 107109137, filed on Mar. 16, 2018. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION Field of the Invention

The invention relates to a sensing apparatus, and more particularly, toa fingerprint-sensing apparatus suitable for fingerprint recognition.

Description of Related Art

A thermal fingerprint-sensing apparatus has advantages such asresistance to pollution and interference caused by an electromagneticsignal and lack of an external optical system compared to an opticalfingerprint-sensing apparatus and a capacitive fingerprint-sensingapparatus. Therefore, the thermal fingerprint-sensing apparatus hasgradually gained attention.

In general, the thermal fingerprint-sensing apparatus requires aplurality of heatable devices such that a plurality of heating devicesis maintained at a specified sensing temperature. The heating devicescan have different heat dissipation speeds corresponding to afingerprint ridge or fingerprint valley, such that the sensingtemperature of the heating devices can generate different temperaturevariations according to the fingerprint ridge or fingerprint valley toachieve the recognition effect of the fingerprint ridge or fingerprintvalley.

However, the thermal fingerprint-sensing apparatus requires a heatingcircuit to main the plurality of heating devices at a specified sensingtemperature. Moreover, when the thermal fingerprint-sensing apparatus issensing a fingerprint, if the sensing time is too long, then the thermalfingerprint-sensing apparatus reaches thermal equilibrium, and as aresult, the thermal fingerprint-sensing apparatus reduces therecognition effect of the fingerprint ridge or fingerprint valley.

SUMMARY OF THE INVENTION

The invention provides a fingerprint-sensing apparatus. Thefingerprint-sensing apparatus of the invention does not require aheating device and a heating circuit, and can effectively reduce thesensing time of an entire fingerprint.

The fingerprint-sensing apparatus of the invention includes afingerprint-sensing pixel array and a plurality of read-out circuits.The fingerprint-sensing pixel array has a plurality offingerprint-sensing pixel columns, and each of the plurality offingerprint sensing pixel columns includes a plurality offingerprint-sensing pixels. Each of the plurality of fingerprint-sensingpixels includes a scanning switch and a thermosensitive currentgeneration circuit. The scanning switch is respectively controlled by arow scanning signal to be turned on or off. The thermosensitive currentgeneration circuit generates a the insensitive current according to thefingerprint-sensing pixel corresponding to a fingerprint ridge or afingerprint valley. The plurality of read-out circuits is respectivelycoupled to the plurality of fingerprint-sensing pixel columns, whereineach of the plurality of read-out circuits receives the thermosensitivecurrent provided by the fingerprint-sensing pixel corresponding to thescanning switch that is turned on via the scanning switch and generatesa fingerprint-sensing signal according to the thermosensitive current.The scanning switches of the plurality of fingerprint-sensing pixels inthe same row of the fingerprint-sensing pixel array are controlled bythe same row scanning signal.

Based on the above, the fingerprint-sensing apparatus of the inventionincludes a fingerprint-sensing pixel array and a plurality of read-outcircuits. The fingerprint-sensing pixel array has a plurality offingerprint-sensing pixel columns. The read-out circuits receive thethermosensitive current provided by the thermosensitive currentgeneration circuit and generate a fingerprint-sensing signal accordingto the thermosensitive current. Therefore, the fingerprint-sensingapparatus does not require a heating device and a heating circuit.Moreover, the scanning switches of the plurality of fingerprint-sensingpixels in the same row of the fingerprint-sensing pixel array arecontrolled by the same row scanning signal, and therefore thefingerprint-sensing apparatus of the invention can effectively reducethe sensing time of an entire fingerprint.

In order to make the aforementioned features and advantages of thedisclosure more comprehensible, embodiments accompanied with figures aredescribed in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is a schematic of a fingerprint-sensing apparatus shown accordingto an embodiment of the invention.

FIG. 2 is a schematic of a fingerprint-sensing apparatus shown accordingto another embodiment of the invention.

FIG. 3 is a schematic of the operation waveform of a fingerprint-sensingapparatus shown according to an embodiment of the invention.

FIG. 4 is a schematic of a fingerprint-sensing apparatus shown accordingto yet another embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1, FIG. 1 is a schematic of a fingerprint-sensingapparatus shown according to an embodiment of the invention. In theembodiment of FIG. 1, a fingerprint-sensing apparatus 100 includes afingerprint-sensing pixel array PA and read-out circuits 110_1 to 110_M.The fingerprint-sensing pixel array PA has fingerprint-sensing pixelcolumns C_1 to C_M. The fingerprint-sensing pixel column C_1 includesfingerprint-sensing pixels P11 to P1N, and the fingerprint-sensing pixelcolumn C_2 includes fingerprint-sensing pixels P21 to P2N . . . etc. Inthe present embodiment, fingerprint-sensing pixels P11 to PM1 in thesame row in the fingerprint-sensing pixel array PA receive a rowscanning signal RS1 via a row scanning line SL_1, andfingerprint-sensing pixels P12 to PM2 in the same row in thefingerprint-sensing pixel array PA receive a row scanning signal RS2 viaa row scanning line SL_2 . . . etc. The read-out circuit 110_1 iscoupled to the fingerprint-sensing pixel column C_1 via a read-outsignal line POL_1, and the read-out circuit 110_2 is coupled to thefingerprint-sensing pixel column C_2 via a read-out signal line POL_2 .. . etc. In particular, M and N are natural numbers greater than 1. Insome embodiments, row scanning signals RS1 to RSN can be generated via aplurality of shift registers connected in series, but the invention isnot limited thereto.

Each of the fingerprint-sensing pixels P11 to PMN includes a scanningswitch and a thermosensitive current generation circuit. For instance,in FIG. 1, the fingerprint-sensing pixel P11 includes a scanning switch120 and a thermosensitive current generation circuit 130. The scanningswitch 120 receives the row scanning signal RS1 via the row scanningline SL_1, and the scanning switch 120 is controlled by the row scanningsignal RS1 to be turned on or off. The scanning switch 120 can be anyform of transistor switch. The thermosensitive current generationcircuit 130 of the fingerprint-sensing pixel P11 generates athermosensitive current according to the fingerprint-sensing pixel P11corresponding to a fingerprint ridge or a fingerprint valley of afingerprint. The read-out circuit 110_1 receives a thermosensitivecurrent provided by the fingerprint-sensing pixel P11 via the scanningswitch 120 that is turned on and the read-out signal line POL_1.Moreover, the read-out circuit 110_1 generates a fingerprint-sensingsignal according to the thermosensitive current. Therefore, thethermosensitive current generation circuit 130 of thefingerprint-sensing pixel P11 can generate a thermosensitive currentaccording to the fingerprint-sensing pixel P11 corresponding to afingerprint ridge or a fingerprint valley of a fingerprint. The read-outcircuit 110_1 generates a fingerprint-sensing signal according to thethermosensitive current. As a result, the fingerprint-sensing apparatus100 does not require a heating device and a heating circuit to achievethe effect of fingerprint sensing.

Moreover, it should be mentioned that, in the present embodiment, thescanning switches of the fingerprint-sensing pixels in the same row(such as the fingerprint-sensing pixels P11 to PM1) of thefingerprint-sensing pixel array PA are controlled by the same rowscanning signal (such as the row scanning signal RS1). Therefore, thescanning switches of the fingerprint-sensing pixels in the same row canbe turned on or off at the same time, and the scanning switches of thefingerprint-sensing pixels in different rows are not turned on or off atthe same time. As a result, the read-out circuits 110_1 to 110_M canreceive the thermosensitive current provided by the fingerprint-sensingpixels in the same row row-by-row to further generate a plurality offingerprint-sensing signals, and the fingerprint-sensing apparatus 100can effectively reduce the sensing time of an entire fingerprint.

Furthermore, referring to FIG. 2, FIG. 2 is a schematic of afingerprint-sensing apparatus shown according to another embodiment ofthe invention. In the embodiment of FIG. 2, the fingerprint-sensingpixel P1 includes a scanning switch 220 and a thermosensitive currentgeneration circuit 230. The scanning switch 220 has a first terminal, asecond terminal, and a control terminal, and the first terminal of thescanning switch 220 is coupled to the read-out circuit 110. The secondterminal of the scanning switch 220 is coupled to the thermosensitivecurrent generation circuit 230. The control terminal of the scanningswitch 220 is configured to receive the scanning signal RS. Thethermosensitive current generation circuit 230 includes a transistorTFTN and a thermistor RT1. The transistor TFTN is an N-type transistor.The transistor TFTN has a first terminal, a second terminal, and acontrol terminal. The first terminal of the transistor TFTN is coupledto the scanning switch 220. The second terminal of the transistor TFTNis coupled to the first terminal of the thermistor RT1. The controlterminal of the transistor TFTN is configured to receive a bias voltageVB. The bias voltage VB can be, for instance, a DC voltage source. Thetransistor TFTN is operated in a work area in a saturated zone accordingto the bias voltage VB such that the voltage level of the secondterminal of the transistor TFTN can be maintained at a fixed voltagelevel. The thermistor RT1 has a first terminal and a second terminal,the first terminal of the thermistor RT1 is coupled to the secondterminal of the transistor TFTN, and the first terminal of thethermistor RT1 is coupled to a system low voltage GND (such as 0 V). Thethermosensitive current generation circuit 230 can generate athermosensitive current Iout according to the resistance value of thethermistor RT1 and the voltage value of the bias voltage VB. The currentvalue of the thermosensitive current Iout can be obtained according tothe following equation.i_RT1=(v_bias−Vth_TFTN)/r_RT1  (equation 1)

In particular, i_RT1 is the current value of the thermosensitive currentIout, v_bias is the voltage value of the bias voltage VB, Vth_TFTN isthe threshold voltage value of the transistor TFTN, and r_RT1 is theresistance value of the thermistor RT1. In other words, the currentvalue of the thermosensitive current Iout can be changed according tothe variation in the resistance value of the thermistor RT1.

In the present embodiment, when a finger is in contact with thefingerprint-sensing apparatus 200, the fingerprint ridge of the fingeris in direct contact with the fingerprint-sensing apparatus 200, and thefingerprint valley of the finger is not in contact with thefingerprint-sensing apparatus 200. For instance, the temperature of thesensing environment (such as 27 Celsius) is, for instance, less than thetemperature of the human skin surface (such as 36 Celsius to 37Celsius), and the thermistor RT1 is, for instance, a negativetemperature coefficient thermistor. If the fingerprint-sensing pixel P1corresponds to the fingerprint ridge, then the thermistor RT1 generatesa first resistance value corresponding to the fingerprint ridgeaccording to the temperature of the fingerprint ridge. If thefingerprint-sensing pixel P1 corresponds to the fingerprint valley, thenthe thermistor RT1 generates a second resistance value corresponding tothe fingerprint valley according to the temperature of the fingerprintvalley. The temperature of the fingerprint ridge is substantially closeto or equal to the temperature of the human skin surface, and thetemperature of the fingerprint valley is substantially between thetemperature of the sensing environment and the temperature of the humanskin surface (such as 33 Celsius to 35 Celsius). Therefore, in the casethat the temperature of the fingerprint ridge is higher than thetemperature of the fingerprint valley, the first resistance value issubstantially less than the second resistance value. As a result, thecurrent value of the thermosensitive current Iout corresponding to thefingerprint ridge is greater than the current value of thethermosensitive current Iout corresponding to the fingerprint valley.For instance, the temperature of the sensing environment (such as 40Celsius) is, for instance, higher than the temperature of the human skinsurface, and the thermistor RT1 is, for instance, a negative temperaturecoefficient thermistor. As a result, the current value of thethermosensitive current Iout corresponding to the fingerprint ridge isless than the current value of the thermosensitive current Ioutcorresponding to the fingerprint valley. The thermistor RT1 of theinvention can be a negative temperature coefficient thermistor or apositive temperature coefficient thermistor.

In some embodiments, when the fingerprint-sensing pixel P1 does notcorrespond to the fingerprint ridge and fingerprint valley, thethermistor RT1 generates a third resistance value according to theambient temperature (such as 27 Celsius). The thermosensitive currentgeneration circuit 230 generates a thermosensitive current Ioutcorresponding to the ambient temperature according to the bias voltageVB and the third resistance value. The current value of thethermosensitive current Iout corresponding to the ambient temperature isdifferent from the current value of the thermosensitive current Ioutcorresponding to the fingerprint ridge and the current value of thethermosensitive current Iout corresponding to the fingerprint valley.

The read-out circuit 110 includes an operational amplifier 112, aresistor R1, and a capacitor C1. The operational amplifier 112 has aninverting input terminal, a non-inverting input terminal, and an outputterminal. The inverting input terminal of the operational amplifier 112is coupled to the thermosensitive current generation circuit 230 via thescanning switch 220. The non-inverting input terminal of the operationalamplifier 112 is coupled to a reference voltage signal VA. The outputterminal of the operational amplifier 112 is configured to output afingerprint-sensing signal Sse. The resistor R1 is coupled between theinverting input terminal and the output terminal of the operationalamplifier 112. The capacitor C1 is coupled between the inverting inputterminal and the output terminal of the operational amplifier 112. Theoperational amplifier 112 of the read-out circuit 110 can receive thethermosensitive current Iout generated by the thermosensitive currentgeneration circuit 230 via a read-out signal line POL and the scanningswitch 220 that is turned on. In the present embodiment, the referencevoltage signal VA can be a DC voltage. The reference voltage signal VAof the invention can be any form of voltage signal, but is not limitedto the present embodiment.

The operating method of the fingerprint-sensing apparatus is furtherdescribed herein. Referring to both FIG. 2 and FIG. 3, FIG. 3 is aschematic of the operation waveform of a fingerprint-sensing apparatusshown according to an embodiment of the invention. In the embodiments ofFIG. 2 and FIG. 3, in a stop-sensing period T0, the voltage value of thebias voltage VB is in a low-voltage level (such as 0 V) state, and thereference voltage signal VA is also in a low-voltage level (such as 0 V)state (the waveform of the reference voltage signal VA is not shown inthe present embodiment). The transistor TFTN is in an off state due tothe low voltage level of the bias voltage VB, and the reference voltagesignal VA is also in a low-voltage level, and therefore thefingerprint-sensing signal Sse is substantially maintained at thelow-voltage level of the reference voltage signal VA in the stop-sensingperiod T0.

When the stop-sensing period T0 is ended, the voltage level of the biasvoltage VB begins to be raised to a high voltage level (such as 24 V),and the reference voltage signal VA also begins to be raised to a highvoltage level (such as 10 V) to begin entering the first sensing periodT1. In the first sensing period T1, the transistor TFTN of thefingerprint-sensing pixel P1 is operated in the work area in a saturatedzone according to the high voltage level of the bias voltage VB, andtherefore the thermosensitive current generation circuit 230 begins togenerate the thermosensitive current tout according to thefingerprint-sensing pixel P1 corresponding to a fingerprint ridge or afingerprint valley of a finger, and therefore the scanning switch 220 isin an off state. Therefore, the waveform of the first sensing period T1of the fingerprint-sensing signal Sse is equal to the waveform of thereference voltage signal VA. In other words, the voltage level of thefingerprint-sensing signal Sse in the first sensing period T1 issubstantially equal to the voltage level of the reference voltage signalVA.

When the logic level of the row scanning signal RS is raised to a highlogic level, a second sensing period T2 is reached.

In the second sensing period T2, the scanning switch 220 is turned on bythe high logic level of the row scanning signal RS. The operationalamplifier 112 of the read-out circuit 110 can receive thethermosensitive current Iout generated by the thermosensitive currentgeneration circuit 230 via a read-out signal line POL and the scanningswitch 220 that is turned on. The voltage level of thefingerprint-sensing signal Sse in the second sensing period T2 is shownin equation 2 below.VH=v_VA+(i_RT1)×r_R1  (equation 2)

In particular, VH is the voltage value of the fingerprint-sensing signalSse in the second sensing period T2, v_VA is the voltage level of thereference voltage signal VA, and r_R1 is the resistance value of thethermistor RT1. In other words, when the scanning switch 220 is turnedon in the second sensing period T2, the read-out circuit can generatethe fingerprint-sensing signal Sse according to the resistor R1, thethermosensitive current Iout, and the reference voltage signal VA. Next,equation 1 and equation 2 are combined to obtain equation 3 as shownbelow.VH=v_VA+(v_bias−Vth_TFTN)×r_R1/r_RT1  (equation 3)

Based on equation 2 or equation 3, in the second sensing period T2, ifthe current value of the thermosensitive current Iout corresponding tothe fingerprint ridge is greater than the current value of thethermosensitive current Iout corresponding to the fingerprint valley,then the voltage value VH of the fingerprint-sensing signal Ssecorresponding to the fingerprint ridge is greater than the voltage valueVH of the fingerprint-sensing signal Sse corresponding to thefingerprint valley. On the other hand, if the current value of thethermosensitive current Iout corresponding to the fingerprint ridge isless than the current value of the thermosensitive current Ioutcorresponding to the fingerprint valley, then the voltage value VH ofthe fingerprint-sensing signal Sse corresponding to the fingerprintridge is less than the voltage value VH of the fingerprint-sensingsignal Sse corresponding to the fingerprint valley. As a result, thefingerprint-sensing apparatus 200 can determine whether thefingerprint-sensing pixel P1 corresponds to the fingerprint ridge or thefingerprint valley according to the voltage value VH of thefingerprint-sensing signal Sse in the second sensing period T2.

In some embodiments, the fingerprint-sensing apparatus 200 can furthergenerate a voltage value VH of the fingerprint-sensing signal Sse notcorresponding to the fingerprint ridge and the fingerprint valley whenthe fingerprint-sensing pixel P1 does not correspond to the fingerprintridge and the fingerprint valley. The voltage value VH of thefingerprint-sensing signal Sse corresponding to the ambient temperatureis different from the voltage value VH of the fingerprint-sensing signalSse corresponding to the fingerprint ridge and the voltage value VH ofthe fingerprint-sensing signal Sse corresponding to the fingerprintvalley. Therefore, the fingerprint-sensing apparatus 200 can furtherdetermine whether the fingerprint-sensing pixel P1 corresponds to thefingerprint ridge, the fingerprint valley, or is not in contact with afinger according to the voltage value VH of the fingerprint-sensingsignal Sse in the second sensing period T2.

Referring to FIG. 4, FIG. 4 is a schematic of a fingerprint-sensingapparatus shown according to another embodiment of the invention.Different from FIG. 2, a thermosensitive current generation circuit 430of a fingerprint-sensing apparatus 400 of FIG. 4 includes a transistorTFTP and a thermistor RT2. The transistor TFTP is a P-type transistor.The transistor TFTP has a first terminal, a second terminal, and acontrol terminal. The first terminal of the transistor TFTP is coupledto a system low voltage GND, and the second terminal of the transistorTFTP is coupled to the first terminal of the thermistor RT2. The controlterminal of the transistor TFTP is configured to receive a bias voltageVB. In the present embodiment, the bias voltage VB can be, for instance,a DC voltage source (such as −24 V). The transistor TFTP is operated ina work area in a saturated zone according to the bias voltage VB suchthat the voltage level of the second terminal of the transistor TFTP canbe maintained at a fixed voltage level. The thermistor RT2 has a firstterminal and a second terminal, the first terminal of the thermistor RT2is coupled to the second terminal of the transistor TFTP, and the firstterminal of the thermistor RT2 is coupled to the second terminal of ascanning switch 420. The thermosensitive current generation circuit 430can generate a thermosensitive current Iout according to the resistancevalue of the thermistor RT2 and the voltage value of the bias voltageVB. The current value of the thermosensitive current Iout can beobtained according to the following equation:i_RT2=(−v_bias+Vth_TFTP)/r_RT2  (equation 4)

In particular, i_RT2 is the current value of the thermosensitive currentIout, v_bias is the voltage value of the bias voltage VB, Vth_TFTP isthe threshold voltage value of the transistor TFTP, and r RT2 is theresistance value of the thermistor RT2. The embodiment details of theread-out circuit 110 of the fingerprint-sensing apparatus 400 and theoperating method thereof are provided in in FIG. 2 and FIG. 3 and aretherefore not repeated herein.

Based on the above, the fingerprint-sensing apparatus of the inventionincludes a fingerprint-sensing pixel array and a plurality of read-outcircuits. The fingerprint-sensing pixel array has a plurality offingerprint-sensing pixel columns. The read-out circuits receive thethermosensitive current provided by the thermosensitive currentgeneration circuit and generate a fingerprint-sensing signal accordingto the thermosensitive current. Therefore, the fingerprint-sensingapparatus does not require a heating device and a heating circuit.Moreover, the scanning switches of the plurality of fingerprint-sensingpixels in the same row of the fingerprint-sensing pixel array arecontrolled by the same row scanning signal, and the plurality ofread-out circuits can receive the thermosensitive current provided bythe fingerprint-sensing pixels in the same row row-by-row to generate aplurality of fingerprint-sensing signals. As a result, thefingerprint-sensing apparatus can effectively reduce the sensing time ofan entire fingerprint.

Although the invention has been described with reference to the aboveembodiments, it will be apparent to one of ordinary skill in the artthat modifications to the described embodiments may be made withoutdeparting from the spirit of the invention. Accordingly, the scope ofthe invention is defined by the attached claims not by the abovedetailed descriptions.

What is claimed is:
 1. A fingerprint-sensing apparatus, comprising: afingerprint-sensing pixel array having a plurality offingerprint-sensing pixel columns, wherein each of thefingerprint-sensing pixel columns comprises a plurality offingerprint-sensing pixels, and each of the fingerprint-sensing pixelscomprises: a scanning switch controlled by a row scanning signal to beturned on or off; and a thermosensitive current generation circuitgenerating a thermosensitive current according to thefingerprint-sensing pixel corresponding to a fingerprint ridge or afingerprint valley, wherein the thermosensitive current generationcircuit comprises: a transistor, wherein the transistor has a firstterminal, a second terminal, and a control terminal, the first terminalof the transistor is coupled to the scanning switch, and the controlterminal of the transistor is configured to receive a bias voltage; anda thermistor, wherein the thermistor has a first terminal and a secondterminal, the first terminal of the thermistor is coupled to the secondterminal of the transistor, and the first terminal of the thermistor iscoupled to a system low voltage; and a plurality of read-out circuitsrespectively coupled to the fingerprint-sensing pixel columns, whereineach of the read-out circuits receives the thermosensitive currentprovided by the fingerprint-sensing pixel corresponding to the scanningswitch that is turned on via the scanning switch and generates afingerprint-sensing signal according to the thermosensitive current,wherein the scanning switches of the fingerprint-sensing pixels in asame row of the fingerprint-sensing pixel array are controlled by thesame row scanning signal.
 2. The fingerprint-sensing apparatus of claim1, wherein the scanning switch has a first terminal, a second terminal,and a control terminal, the first terminal of the scanning switch iscoupled to each of the read-out circuits respectively, the secondterminal of the scanning switch is coupled to the thermosensitivecurrent generation circuit, and the control terminal of the scanningswitch is configured to receive the row scanning signal.
 3. Thefingerprint-sensing apparatus of claim 1, wherein when thefingerprint-sensing pixel corresponds to the fingerprint ridge, a firstresistance value is generated according to a temperature of thefingerprint ridge, and when the fingerprint-sensing pixel corresponds tothe fingerprint valley, a second resistance value is generated accordingto a temperature of the fingerprint valley.
 4. The fingerprint-sensingapparatus of claim 1, wherein the transistor is operated in a work areain a saturated zone according to the bias voltage.
 5. Thefingerprint-sensing apparatus of claim 1, wherein the thermosensitivecurrent generation circuit generates a first thermosensitive currentcorresponding to the fingerprint ridge according to the bias voltage anda first resistance value and generates a second thermosensitive currentcorresponding to the fingerprint valley according to the bias voltageand a second resistance value, wherein a current value of the firstthermosensitive current is greater than a current value of the secondthermosensitive current.
 6. The fingerprint-sensing apparatus of claim1, wherein when the fingerprint-sensing pixel does not correspond to thefingerprint ridge and the fingerprint valley, the thermistor generates athird resistance value according to an ambient temperature and thethermosensitive current generation circuit generates a thirdthermosensitive current according to the bias voltage and the thirdresistance value.
 7. The fingerprint-sensing apparatus of claim 1,wherein each of the read-out circuits comprises: an operationalamplifier having an inverting input terminal, a non-inverting inputterminal, and an output terminal, wherein the inverting input terminalof the operational amplifier is coupled to the thermosensitive currentgeneration circuit via the scanning switch, the non-inverting inputterminal of the operational amplifier receives a reference voltagesignal, and the output terminal of the operational amplifier isconfigured to output the fingerprint-sensing signal; a resistor coupledbetween the inverting input terminal and the output terminal of theoperational amplifier; and a capacitor coupled between the invertinginput terminal and the output terminal of the operational amplifier. 8.The fingerprint-sensing apparatus of claim 7, wherein when the scanningswitch is turned on, each of the read-out circuits generates thefingerprint-sensing signal according to the resistor, thethermosensitive current, and the reference voltage signal.
 9. Thefingerprint-sensing apparatus of claim 7, wherein when the scanningswitch is turned off, each of the read-out circuits generates thereference voltage signal.